可撓曲及具有摻鎵氧化鋅奈米針結構發光二極體的光學特性研究

Optical Characterizations of Light-emitting Diodes with Bendable Structures and Ga-doped ZnO Nanoneedles

朱鶴鳴(Erwin Zhu)

指導教授 ： 楊志忠

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.00135

摘要

在本論文中，我們透過光學特性分析比較了發光二極體在六種不同基板結構的發光行為，包括成長在藍寶石基板上的側向式發光二極體、晶圓鍵合於矽基板的垂直式發光二極體、銀膠黏著在鐵金屬平板的可撓式的發光二極體以及銀膠黏著在三種不同曲率半徑的圓柱鐵棒上的可撓式發光二極體。拉曼光譜的量測結果顯示可撓式發光二極體因氮化鎵層無法緊密接合基板而有較強的舒張應力，此導致量子侷限史塔克效應變弱，因此發光效率增強。這種現象在金屬彎曲曲率半徑較小時特別顯著。另外我們透過光學特性分析探討了在表面具有銀奈米顆粒及氧化鎵鋅透明導電層的發光二極體，此結構可以結合表面電漿子耦合、電流擴散、光萃取和減少接觸電阻的機制來增強發光效率。在較高的成長溫度下(350 oC)，銀奈米顆粒可以當作成長氧化鎵鋅奈米針的催化劑，此奈米針可以使光萃取效率增加。此時，埋在氧化鎵鋅層下殘存的銀奈米顆粒可以產生表面電漿子耦合效果。在較低的氧化鎵鋅成長溫度下(250 oC)，無法形成氧化鎵鋅奈米針，但可以保存所有的銀奈米顆粒而產生較強的表面電漿子耦合效果。在製作銀奈米顆粒前先於p-型氮化鎵上成長經過熱退火的薄氧化鎵鋅中間層，此中間層可以減少在氧化鎵鋅和p-型氮化鎵之間的接觸電阻率，因此元件的電阻可以降低。

關鍵字

發光二極體 ； 可撓曲 ； 摻鎵氧化鋅 ； 奈米針

並列摘要

Through optical characterizations, the emission behaviors of six light-emitting diodes (LEDs) of different substrate structures, including a lateral LED grown on sapphire substrate, a vertical LED wafer-bonded onto Si (111) substrate, a bendable LED Ag-epoxied onto a flat iron plate, and another three bendable LEDs Ag-epoxied onto circular iron rods of different radii of curvature are compared. The results of Raman scattering measurements show that a stronger tensile strain is generated in a bendable LED for reducing the QCSE and hence increasing emission efficiency when the epitaxial layer is not tightly bonded onto a hard substrate. Such a behavior is particularly stronger when the bending radius of curvature is smaller. Also, through optical characterizations, the combined effects of a few mechanisms for emission efficiency enhancement generated in the overgrowth of a transparent conductor layer of GaZnO on a surface Ag-nanoparticle (NP) coated LED, including surface plasmon (SP) coupling, current spreading, light extraction, and contact resistivity reduction are demonstrated. With a relatively higher GaZnO growth temperature (350 oC), Ag NPs can be used as catalyst for forming GaZnO nanoneedles (NNs) such that light extraction efficiency can be increased. In this situation, certain residual Ag NPs are buried in the simultaneously grown GaZnO layer for inducing SP coupling. With a relatively lower GaZnO growth temperature (250 oC), all the Ag NPs are preserved for generating a stronger SP coupling effect. By using a thin annealed GaZnO interlayer on p-GaN before Ag NP fabrication, the contact resistivity at the GaZnO/p-GaN interface and hence the overall device resistance can be reduced.

並列關鍵字

Light-emitting Diodes ； Bendable ； GaZnO ； Nanoneedles

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